(1) Field of the Invention
The present invention relates to a sheet discharge mechanism provided for an ink jet printer for forming a designated image on a sheet of paper with ink ejected from an ink head.
(2) Description of the Prior Art
In an ink jet printer in which an image is formed on a sheet of paper with ejected ink from an ink head, the sheets with images formed with ink are discharged and stacked one over another on the sheet output tray. Therefore, when images are recorded continuously on a multiple number of sheets, a sheet having an image formed with ink is laid over the previous one before its ink dries so that the sheets may be stained or the image of ink may be disrupted by contact of the undried sheet. To avoid this, continuous image forming may be performed at intervals of a time which allows for drying of the ink on the sheet. However, drying of the ink on the sheet usually needs about 40 to 60 seconds, which makes high-speed image forming impossible.
In order to solve this problem, there has been a known printer inside which a drying device for drying the ink of the image formed on the paper is provided. However, provision of such a drying device therein makes the printer body bulky and degrades its economy.
Japanese Patent Application Laid-Open Hei 6 No.91861 discloses an ink jet printer in which when a sheet of paper having an image formed with ink is discharged from the printer body, the sheet being discharged is forcibly curved so as to be projected downward with respect to the direction perpendicular to the direction of discharge of the paper. In this way, curving the paper being discharged from the printer body can prevent the leading end, with respect to the direction of discharge, of the sheet from bending or drooping downwards so that the sheet can be kept horizontal until the sheet is discharged completely from the printer body. Therefore, the sheet being discharged can be held over the sheet previously discharged for an appropriate period of time and then stacked on the sheet output tray, thus making it possible to lengthen the time for the sheet to drop onto the sheet output tray and hence dry the ink on the previous sheet on the sheet output tray.
However, even with such a configuration in which a sheet is discharged from the printer body by being curved so as to be kept horizontal, there is a fear that the sheet may droop without being kept horizontal if the sheet itself has low rigidity and can be readily flexed so that the sheet may come in contact with the previous sheet on the sheet output tray and stain the sheet being discharged or disrupt the image on the previous sheet. This problem also occurs when a large sized sheet is used.